"The driving factor for the committee's decision was fundamental fairness," Irene Keeley, a district judge in West Virginia, recently testified. "We do not believe that the date a sentence was imposed should dictate the length of imprisonment."

The Justice Department has sought more leniency for some non-violent drug offenders in hopes of reducing sentencing disparities dating from the crack cocaine epidemic of the 1980s.

The department, however, preferred a more limited approach than the Sentencing Commission has taken, arguing that only lower-level, nonviolent drug offenders without significant criminal histories should be eligible. That would have reduced the number of inmates who could petition for early release to about 20,000.

Although its guidelines are just that — non-binding recommendations — they hold great sway within the judiciary.

Prosecutors have expressed concern about the direction the commission is going. "The strong sentencing scheme that has been in place over the last 25 years in our country has contributed to the lowest crime rates in more than a generation," the National Association of Assistant United States Attorneys wrote in a letter to the commission.